Angularly Stable Fixation Of An Implant

ABSTRACT

A system and method of angularly stable fixation of an implant on a bone includes the steps of making at least one hole in the bone by means of a bone drill. An implant is placed on the bone in a desired position and joining the implant with the bone, such that the implant is prevented from rotation about its attachment point. A system is provided for use in the above described method. The system comprises a bone drill, an implant and a sonotrode for angularly stable fixation of the implant on the bone. The system can further comprise a joining element to join the implant with the bone.

CROSS REFERENCE TO RELATED APPLICATION

The present application is a national phase entry under 35 U.S.C. §371of International Application No. PCT/EP2007/008130, filed Sep. 18, 2007,published in English. The disclosure of said application is incorporatedby reference herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a system and method of fixation of an implantto a bone. The invention particularly relates to a system and method ofangularly stable fixation of an implant to a bone.

2. Brief Description of the Prior Art

It is generally known that fractures are treated by fixation of thebroken bones. The individual fragments of the bone are lined up to eachother so that the separated parts can grow together again. It isnecessary that the parts remain relatively stable with respect to eachother over a time period to allow the healing. It is possible in manycases to fix the fragments of the fractured bone via a rigid cast suchas a plaster cast on the outside of the broken part of the body. Thebroken bone pieces are aligned with each other and held in position bythe rigid cast. In some cases, particularly for more complicatedfractures, it is necessary to connect the individual broken bone piecesdirectly with each other. In these cases, the fracture is fixed orreduced via an invasive procedure wherein an implant is installed withinthe body with screws or nails.

It has turned out, however, that fixed bone parts do not always growtogether as desired. In addition, the conventional invasive methods offracture fixation are accompanied by relatively high trauma and loss ofblood. Furthermore, there is a need for a device for fixation ofperiprothetic fractures in immediate proximity of implants, particularlyjoint implants.

Fixing plates have been suggested for use in the methods mentionedabove. Plates are first pre-formed according to the individual fracturesituation outside the patient and then connected via an operation to thefractured bone or the bone fragments by nails or screws. These plateshave the additional advantage that they can fix particularly smallerfragments and stabilize the fracture. This way, in case of morecomplicated fractures, the fractured pieces can be reliably connectedwith each other or with several fragments.

However, these fixing plates cannot be fastened ideally. Particularlywhen the fracture involves the musculoskeletal system and the fracturedpieces are exposed to different shearing forces in the course of themovement. Thus, there is a need for implants with improved fixation forfractures involving musculoskeletal system.

SUMMARY OF THE INVENTION

The present invention provides a system comprising an implant plate froma polymeric material, a bone drill and a sonotrode. The system furthercomprises a pin from a polymeric material, which is provided to join theimplant plate with the bone. The pin can be selected from the groupconsisting of a pin, a conically formed pin, a plug, a springing up hookplug, a multi-toothed plug, a screw, a conically formed screw, a gradedpin, a twice formed pin, a triangular formed or asymmetrically formedpin, or a pin having a thickened head. In case the polymeric pin shallbe melted together with the implant, the implant material should be thesame or at least similar to the material of the polymeric pin.

According to an exemplary embodiment the present invention provides asystem that includes a plate having an opening formed therein. Theopening is rotationally non-symmetric. The system also includes a drill.The drill is adopted to form the opening and a hole in a bone adjacentthe plate. The system further includes a pin insertable in the opening.A sonotrode is also included in the system. The sonotrode is adapted toapply energy to the pin so as to melt at least a portion of the pinthereby attaching the pin in the bone and to the plate such thatrotational movement of the plate is prevented.

Yet another embodiment of the invention provides an angularly stableimplant for fracture fixation. The implant includes a plate adapted tomount on a bone. The plate and the bone have a first opening and asecond opening respectively. The first opening and the second openingare substantially aligned and have a rotationally non-symmetric shape. Apin shaped to be inserted in the first opening and second opening andcapable of receiving energy to melt at least a portion of the pin isprovided. The melted material of the pin is capable of solidifying inthe first opening and the second opening to weld the pin to the bone andthe plate to form an angularly stable implant that does not rotate withrespect to the bone.

The invention also includes a method generally having the followingsteps: Making at least one hole in the bone, connecting an implant withthe bone angle stably at a desired position at the bone and finallyplacing the implant. In accordance with an exemplary embodiment a jigcan be used at the method to establish at least one hole in the bone oralso lead means with the help of which the implant is fastened to thebone angle stably. In accordance with a further exemplary embodiment amarking can be set, which at first serves to line up the jig or thematrix on the bone for preparing the at least one hole in the bone, andthen to align with the marking and place thus exactly the implant. Inaccordance with another exemplary embodiment of the method according tothe invention the implant material is liquefied by applying ultrasoundenergy to the material so that the implant material flows into the atleast one hole and fixes the angular stability of the implant placed atthe bone. By the ultrasound energy also a joining element can beliquefied, which is placed through the implant and into the at leasthole formed in the bone, so that it is, on the one hand, reliablyestablished in the bone and, on the other hand, melted together with theimplant material at its back end.

According to another embodiment the present invention also includes amethod of fracture fixation wherein the implant is placed on the bone,the implant having a first vertical axis normal to a top surface of theimplant. A first and a second hole are drilled in the bone, the firsthole and the second hole forming a first angle and a second anglerespectively with the vertical axis. At least a portion of the implantis melted and pushed in the first hole and the second hole. The meltedimplant material is allowed to solidify in the first hole and the secondhole to obtain an angularly stable attachment of the implant to thebone.

Another method of fracture fixation teaches placing a plate on a boneand forming at least one opening in the plate and the bone. The openingis rotationally non-symmetric. A pin is inserted in the opening andenergy is applied to the pin to melt at least a portion of the pinthereby attaching the pin in the bone and to the plate such thatrotational movement of the plate is prevented.

Another method of fracture fixation teaches placing a plate on a bonethe plate having a vertical axis extending through the thickness of theplate. Forming in the bone a first opening at a first angle with theaxis and a second opening at a second angle with the vertical axis.Melting the plate by application of energy and flowing the meltedmaterial of the plate in the first opening and the second opening toform an angularly stable connection between the plate and the bone uponsolidification.

It is an object of the invention to provide a system and a method offixation of an implant plate to a bone, in which the implant plate isconnected with the bone in an angularly stable manner.

This object is achieved by the subject matter of each independent claim.Further exemplary embodiments are described in the respective dependentclaims.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is explained by means of exemplary embodiment and withreference to the following drawings.

FIG. 1 shows schematically, in four frames, a method of angularly stablefixation of an implant on a bone in accordance with a first exemplaryembodiment of the invention.

FIG. 2 shows schematically a second exemplary embodiment of a method inaccordance with the invention.

FIG. 3 shows schematically a third exemplary embodiment of a method inaccordance with the invention.

FIG. 4 shows schematically a fourth exemplary embodiment of a method inaccordance with the invention.

FIG. 5 shows schematically a fifth exemplary embodiment of a method inaccordance with the invention.

FIG. 6 shows schematically a sixth exemplary embodiment of a method inaccordance with the invention.

FIG. 7 shows schematically a seventh exemplary embodiment of a method inaccordance with the invention.

FIG. 8 shows schematically an eighth exemplary embodiment of a method inaccordance with the invention.

FIG. 9 shows schematically a ninth exemplary embodiment of a method inaccordance with the invention.

FIG. 10 shows schematically a tenth exemplary embodiment of a method inaccordance with the invention.

DETAILED DESCRIPTION

FIG. 1 shows an implant plate 20 mounted directly on cortical bone 10.The implant plate 20 may be made from materials such as medical gradeplastic, for example, from a polylactid material (PLLA, PLDLA). The usedmaterial might be resorbable. Each one of the FIGS. 1-10 has four framesshowing the steps of the method illustrated in each of the figures. Theimplant plate 20 and the bone 10 are drilled through with the help of aKirschner wire 40 such that the drilled openings 11 and 12 cross eachother. The drilled openings 11 and 12 should preferably cross at theinterface of the implant plate 20 and the bone 10. A drill jig 30 orother suitable guiding device can be used to guarantee that the crossingpoint is at the interface of the plate 20 and the bone 10. Asrepresented in frame 1 in FIG. 1, the implant plate 20 is placed on thebone 10. The jig 30 is placed on the plate 20. The jig 30 has twochannels 31 and 32 through which a Kirschner wire or alternatively adrill can be advanced to drill openings 11 and 12. Furthermore, the jig30 has a through hole 33, which accepts and guides a sonotrode.

First the Kirschner wire 40 is reciprocated back and forth through thechannel 31 of the jig 30 to form a first opening 11 both through theimplant plate 20 and through the bone 10. Next, the Kirschner wire 40 isreciprocated back and forth, as seen in frame 2 in FIG. 1, through thesecond channel 32 of the jig 30 so that a second opening 12 is formed inthe implant plate 20 and the bone 10. The two openings 11, 12 cross atthe interface plane between the implant plate 20 and the bone 10.

As shown in frame 3 in FIG. 1 the jig 30 is located on the implant plate20. Next, by means of a sonotrode 50 led in the through hole 33, apressure force F and a vibration U is applied, so that the implantmaterial of the implant plate 20 liquefies in the area of the drilledopenings 11, 12 and a part of the material flows into these openings. Byvirtue of the material flowing in the openings 11 and 12, the plate 20is fixed to the bone 10 as shown in frame 4. The plate 20, fixed to thebone 10, in the above described manner is angularly stable, i.e., theplate cannot rotate. The inclination of the channels 31, 32 in the jig30 are dependent on the thickness of the implant plate 20. The boneplate 20 is received in the bone 10 like the root of a tooth in the jaw.A variation of this exemplary embodiment of the method may have fourdrillings/openings placed at 90 degrees from each other instead of thetwo opposite drillings. The thickness of plate 20 may be thicker orthinner as required. This way more polymer can flow into the openings 11and 12 in the bone 10. The aim is to have sufficient plate thicknessleft after the impact of the pressure force F and the ultrasoundvibrations U has produced ample melting of the plate 20. Through thisshear stress can be avoided at later load.

FIG. 2 shows a second exemplary embodiment of the invention. Here theimplant plate 20 is connected with the bone 10 in an angularly stablemanner. Frame 1 shows a drill jig 30 a placed on the bone 10. Next, amarking 15 is placed on the bone 10. Then a tapped hole 13 is cut intothe bone 10 by means of a screw drill or tap 40 as shown in frame 2 inFIG. 2. The screw drill 40 is inserted in and guided by opening 35 inthe jig 30 a to form the tapped hole 13 in the bone 10. The marking 15is then used to place the implant 20 together with the jig 30 a in thedesired location. Next the sonotrode 50 is aligned with the opening 35in the jig 30 a which was already used for making hole 13 using thescrew tap 40. Frame 3 in FIG. 2 shows use of the sonotrode 50 to melt(i.e., liquefy) the material of the implant plate 20 and flow the meltedmaterial into the threaded hole 13 in the bone 10. The melting is doneby applying pressure F and the vibrations U to the implant 20 via thesonotrode 50. Frame 4 of FIG. 2 shows the implant 20 attached to bone 10using the method illustrated in FIG. 2.

Unlike the first exemplary embodiment no opening/hole is cut into theimplant plate 20 itself and consequently formation of polymer debris isprevented. Here only the bone 10 is provided with a threaded hole 13.The drilling point and the point to which the sonotrode 50 is attachedis defined by a jig 30 a which is aligned with the marking 15. Theprocess described above may be repeated to form more than one holes, inwhich the implant material then flows into and stiffens. The sonotrode50 produces the energy by means of ultrasound vibrations U and a force Fwhich is suitable to liquefy the implant material in the area of thethreaded opening 13. The location of the threaded hole 13 is visible asa slight depression 25 in the implant plate 20 where the sonotrode 50was in contact with the implant plate 20. This depression 25 can beavoided or at least the expression reduced by strengthening the materialof the plate 20 at the respective impact point of the sonotrode.

FIG. 3 shows a third exemplary embodiment that illustrates the methodaccording to the invention. The third embodiment uses pre-formed implantplate 20. The plate 20 has the geometry that also fulfils the functionsof the polymeric pins of other exemplary embodiments. The implant plate20 of the third exemplary embodiment comprises protrusions 22 that aresized to be slid into holes 13 in the bone 10. The location of theprotrusions 22 in the implant plate 20 requires a very exact andcorresponding positioning of thread holes 13 in the bone 10. This can bemanaged, for example, by means of a jig 30 b.

As shown in frame 1 in FIG. 3, first the jig 30 is placed on the bone10. Next, threaded openings 13 are formed in the bone 10 using screw tap40. The holes 35 in the jig 30 b are used to guide screw tap 40 duringformation of openings 13. Next, the implant plate 20 is placed on bone10 such that protrusions 22 project into each drilled hole (i.e.,opening) 13. The implant material is now liquefied by means of asonotrode 50 which is formed with a pointed front end that is insertedin the protrusions 22. This results in the implant material being meltedand conforming to the threads formed in the opening 13 in the bone 10,as shown in the frames 2 and 3 in FIG. 3. In this third exemplaryembodiment a preliminary stabilization of the fracture is achieved byinserting the protrusions 22 of the implant plate 20 into the openings13 in the bone 10. The protrusions 22 may be formed in shape of a conewith a central through hole 23, i.e., a through hole 23 may be formedthrough the implant plate 20 and lengthwise through the protrusions 22.The tip of the sonotrode 50 fits into this hole 23. The tip is greaterin diameter than the opening in the plate 20 and does exert a pressureon the implant material not only in axial but also in radial directionwithin the threaded openings 13 in the bone 10 so that the materialflows reliably into the threads of the screw thread in the bone 10. Theimplant 20 of the third embodiment represents a very stable systembecause it only consists of a single component.

Exemplary embodiments described hereafter use an additional joiningelement 60. The joining element 60 is used to connect the implant plate20 with the bone 10. The fourth exemplary embodiment of the presentinvention is schematically represented in four frames of FIG. 4. Aconical screw tap 40 which makes a conical threaded hole 13 in theimplant plate 20 and through the bone 10 simultaneously is shown inframe 1 in FIG. 4. Next, in frame 2, a conical pin 60 is shown insertedinto the hole 13. The cone angle of the conical pin 60 matches the angleof the screw tap 40. Frame 3 in FIG. 4 shows the pin 60 being liquefiedby means of the sonotrode 50. The liquefied material of the pin 60 fillsout the cavities in the threaded opening 13 and also melts together withthe implant material of the implant plate 20. The penetration depth ofthe screw tap 40 depends on the plate thickness and is correspondinglydefined by a stop 41. The threaded opening 13 offers a simplepossibility for the structuring of the bone 10 and at the same timesupports the melt process by creation of defined places with high localenergy density.

FIG. 5 shows successive frames of the fifth exemplary embodiment of theinvention. Similar to the fourth exemplary embodiment, here a hole(alternatively referred to as an opening) 13 is drilled by means of ascrew tap 40 through the implant plate 20 and the bone 10simultaneously. A screw 60 is screwed into this hole 13. This way theimplant plate 20 is preliminarily stabilized in the bone 10. A finalangularly stable attachment of the implant to the bone 10 is achieved byapplying a force F and an ultrasound vibration U by means of a sonotrode50 to the screw 60. Thereby, the screw thread of the screw 60 isliquefied and the liquefied material moulds to conforms to the threadsin the hole 13 in the bone 10. Further the screw head 61 is meltedtogether with the adjacent surface of the implant plate 20.

Since the material of the inserted screw 60 liquefies due to theapplication of the ultrasound vibration U and the force F, the shaft ofthe inserted screw may be made smooth in a variation of this embodiment,i.e. the threads of the threaded pin are optional. In addition, theprocessing of the implant plate 20 and the bone 10 can be done by adrill-tap-combination. The drilling depth is provided by means of adrilling stop 41. The front tap part 43 produces the threaded hole 13 inthe bone 10 and the following drill part 42 of the drill-tap-combinationproduces a smooth hole in the implant plate 20. The material of thepolymeric pin 60 melted and then stiffened in the threaded hole 13,offers a good anchorage of the implant plate 20 in the bone 10. Bywelding together the pin head 61 or the screw head 61 with the implantplate 20 an angularly stable fixation of the implant in the bone 10 isensured.

The sixth exemplary embodiment of the invention is shown in FIG. 6. Thismethod practiced using the sixth embodiment is similar to the method inaccordance with the fifth exemplary embodiment. The difference here isthat in place of the threaded hole 13, a through hole 14 is formed inthe bone 10. The through hole 14 is drilled through the implant plate 20and cortical portion of the bone 10. The simple procedure for preparingof the bone 10 and the implant plate 20 represents a principal benefitof this solution. This simple procedure of making a smooth hole 14 isperformed using a drill 40 as shown in frame 1 in FIG. 6. Next thesurgeon inserts a polymeric pin 60 in the hole 14 and pushes it by meansof a sonotrode 50. The diameter of the polymeric pin 60 is slightlygreater than that of the hole 14 in the bone 10. The diameter differenceideally is about 0.1 to 0.2 mm.

The application of the ultrasound energy via the sonotrode 50 melts thematerial of the pin 60 where the pin 60 comes in contact with the bone10. The melted material is transported by the movement of the pin 60through the hole 14 and below the cortical portion of bone 10. Themelted material stiffens there again and provides a thickening 62 belowthe cortical portion of bone 10 (for example cancellous bone) as aresult of which a reliable anchorage is achieved. The polymeric pin 60is also welded with the polymeric material of the implant plate 20 byvirtue of the fact that the opening in the implant plate 20 and the head61 of the polymeric pin 60 are conical and form a close fit and arewelded together under the action of the ultrasonic energy.

The seventh exemplary embodiment of the invention is shown in FIG. 7. Inthe seventh embodiment, a plug 60 is used instead of a polymeric pin ora screw of the previous embodiments. As shown in frame 1 in FIG. 7, ahole 14 is formed into the implant plate 20 and the bone 10simultaneously. A drill 40 is used to form the hole 14. A plug 60 isinserted in hole 14 as shown in frame 2 in FIG. 7. At first, latches 63which are formed at the leading end of the plug 60 are pressed againstthe shaft 64 of the plug. As soon as the leading edge has penetratedthrough the cortical portion of the bone 10 into the cancellous bone,the latches 63 expand away from the shaft 64 and anchor the plug 60 inthe bone 10.

As illustrated in frame 3 in FIG. 7, the back end of the plug 60 canthen be liquefied by subjecting it to the ultrasonic energy via thesonotrode 50 and thereby welding it to the implant material. The resultis a snap-in connection of the plate 20 with the cortical part of bone10. To prevent the polymeric plug 60 from being pushed during theprocess of welding and consequently becoming loose in the bone 10, acord (not shown) can be provided which is integrated into the plug.Using the cord, the plug 60 can be drawn towards the sonotrode 50 duringthe melting process. This way the plug 60 can be used so that theelastic latches are held under tension against the cortical portion ofbone 10 at the leading edge of the plug 60.

FIG. 8 shows the eighth exemplary embodiment of the invention. In theeighth exemplary embodiment a plug 60 is used for the anchorage of theimplant plate 20 on the bone 10. In this case the plug 60 includes teeth65 on the surface of the shaft portion of the plug 60. The shaft of theplug 60 has a longitudinal slit that allows the shaft to be pressed inradial direction. This allows the plug 60 to be pushed through a hole14, which is smaller in diameter than the shaft diameter of the plug 60in its non-compressed state.

Ideally, a hole is drilled both into the implant plate 20 and into thebone 10 by means of a conical bone drill 40. A stop 41 at the drill 40limits the depth of the hole 14 and prevents it from being formed toodeeply in the bone 10. The implant plate 20 is anchored in the bone 10by inserting the plug 60 deeply into the hole 14. The teeth 65 locatedadjacent to the head of the plug 60 act as hooks which abut the insideof the bone 10. On the other hand, the teeth which are formed along theshaft lodge into the bone within the drilling 14. The plug 60 is welded,by means of a sonotrode 50, with the implant plate 20. The conical shapeof the hole allows anchoring of the plug in the hole 14. A suitably finegeometry of the teeth 65 or lamellae for the anchorage of the plug 60can reduce a play which may arise when the sonotrode 50 is pushed on theplug 60 to weld it together with the implant plate 20.

FIG. 9 shows schematically the ninth exemplary embodiment of theinvention. One feature of this embodiment is the triangular hole 16formed in the bone 10. A hole without rotational symmetry and largerthan the triangular hole 16 is formed in the implant plate 20.Alternatively, non-rotational-symmetric holes of any other shape may beformed in the implant plate 20 and the bone 10. Non-rotational-symmetricholes (or alternatively rotationally non-symmetric holes) are holes inwhich a pin of complimentary shape can not be rotated by virtue of theshape and matching size of the pin and the hole. An example of therotationally non-symmetric hole would be non-circular i.e. an oblonghole or a triangular hole. The matching pins would be oblong ortriangular respectively and would be sized to be a close fit in thehole. The holes may be formed, for example, by means of a drill 40 whichis ground on one side or is swinging eccentrically, as shown in frame 1in FIG. 9. Other known methods available to one skilled in the art maybe used to make the holes. A polymeric pin 60 is then introduced in thehole 16 with a cross section similar to that of the hole 16. Thepolymeric pin 60 has a threaded hole 66 extending in longitudinaldirection in the centre portion of the pin 60. An appropriately formedtip of the sonotrode 50 is connected to the threaded hole 66. Thepolymeric pin 60 is completely screwed on the tip of the sonotrode suchthat it cannot be screwed any further.

Furthermore the length of the pin 60 is such that the pin 60 projectsinto the bone 10 beyond the cortical bone layer. In this position atorque M is applied together with the ultrasound vibration U from thesonotrode 50 and the assembly of sonotrode and polymeric-pin is rotatedby about 60 degrees. Here, a tool combination of a sonotrode and a drillis conceivable.

Finally, the pin 60 would melt in the area that is in the cortical bonelayer of the bone 10. However, the polymeric pin would encounter muchless resistance to rotation in the areas of the pin 60 that extendbeyond the cortical layer of bone 10 at both ends. Since the leadingedge of the pin 60 is in the softer portion of the bone located next tothe cortical bone layer, the rotation of the assembly of sonotrode 50and the pin 60 results in dislocation of the pin portion that is locatedin softer bone and seen in frame 3 of FIG. 9. Similarly, the portion ofthe pin 60 that is located in the implant plate 20 is also dislocated inrelation to the portion of the pin 60 that is adjacent the corticalportion of the bone 10. This way the polymeric pin 60 is locked frombelow the cortical bone layer and on top in the implant plate 20.Therefore, the pin 60 is prevented from being pulled out of the bone 10.Additional locking of the polymeric pin 60 is achieved by melting thepin 60 together with the material of the implant plate 20. As a resultan angularly stable connection of the implant plate 20 to the bone 10 isachieved.

Frame 1 of FIG. 9 illustrates the method step in which a hole 16 isformed in the implant plate 20 and the bone 10. The detail A shows thecross-section of the hole 16. The polymeric pin 60 which is screwed onto the tip of the sonotrode all the way up to the stop and put into thehole 16, is shown in frame 2 of FIG. 9. Detail B shows a cross-sectionalview of the hole 16 with the polymeric pin 60 inserted therein. Frame 3of FIG. 9 shows the condition of the polymeric pin 60 after a torque Mwas applied by the sonotrode 50. Distortion of the end regions of bodyof the pin 60 relative to the central region is visible in the area ofthe implant plate 20 and below the cortical portion of the bone 10.Detail C shows a bottom view of the leading end of the polymeric pin 60which is twisted by 60 degrees relatively to the hole 16. Frame 4 ofFIG. 9 finally shows the polymeric pin in its final position weldedtogether with the implant plate 20.

FIG. 10 shows the tenth exemplary embodiment of the invention. Incontrast to the embodiments described above, the openings 13 of thetenth embodiment are formed in pairs. FIG. 10 shows an instrument 40with two parallel drills which are synchronized contrarily by means of aone-level gear transmission with the translation relationship of 1:1.The drills are used to make openings 13 through the implant plate 20 andthe bone 10 simultaneously. The drills are inserted in the bone 10 untila stop 41 touches the implant plate 20 and prevents the drills fromgoing any further. Openings 13 may be threaded. Next a pin 60 havingcylindrical arms 67 coupled by a bridge 68 is inserted in openings 13.Arms 67 are sized for insertion in the openings 13. Next, a sonotrode 50is brought in contact with the polymeric pin 60.

Sonotrode 50 applies a force F and an ultrasound vibration U to thepolymeric pin 60 as shown in frame 3 of FIG. 10. The ultrasonic energymelts the material of the bracket 60 and the melted material flows intothe threaded holes 13 formed in the bone 10. The pin also melts at theinterface of the pin 60 and the implant plate 10. The melting togetherof the pin 60 with the implant plate 20 forms a stable system with adouble anchorage in the bone 10. To promote the process of melting,spikes 69 are provided on the bridge 68. The spikes create areas of highenergy density and thereby promote melting.

The method and system according to the present invention, allowsfracture stabilization wherein an implant plate is mounted on a bone.The implant plate is angularly stable, i.e., the plate is attached suchthat it would not rotate around the attachment point. The fracturestabilization using the system and method of the invention can becarried out in combination with use of minimally invasive technology. Acomparatively small operation trauma and small loss of blood as well asthe reliable anchorage in an osteoporotic bone can be achieved byangularly stable fixation of implant plates on the bone. The implantskeep their retention force despite unfavourable conditions encounteredin case of complicated fractures until the conclusion of the healing ofthe fractures in the osteoporotic bone. The firm angularly stableconnection between implant, joining element and the bone contributes toa considerably higher primary stability as well as to a lower rate ofloosening.

It is noted that the various aspects of the system and method of theinvention described in context of one embodiment can also be used incombination with the other embodiments of the system and method in whichthey were not explicitly mentioned. The bone can be provided with one,two, three or more holes depending on the situation of the fracture andthe size of the implant plate. The use of a mark to control thepositioning of the implant plate and/or the use of a jig on the implantplate or directly on the bone, for the preparing of the bone holes canbe principally incorporated into each of the described exemplaryembodiments. Additionally, a variation of the form (or shape) of thedrilling in the implant plate and in the bone and of the form (or shape)of the implant plate itself or the polymeric pins coordinated with it,is freely eligible (and envisioned) in each of the mentioned exemplaryembodiments. The bores (or holes or openings or drillings) and thus alsothe form (or shape) of the polymeric pin can be conical, stepped,straight, threaded or smooth or any combination thereof. The material ofthe implant plate as well as the pins of each embodiment might beresorbable. Further, the material might be selected from a polylactidmaterial family, for example from PLLA or PLDLA.

In the following, exemplary embodiments of the invention are described.

A system according to a first embodiment of the invention, for angularlystable fixation of an implant to a bone, comprises a tool for preparingat least one hole in the bone, a sonotrode, a jig for the tool toprepare the at least one hole in a desired position and/or for thesonotrode, and an implant having a material which is fluidizable bymeans of the sonotrode, to angularly stable fixing the implant at thebone.

The tool of the system according to the first embodiment may be selectedfrom the group consisting of a bone drill, a conical bone drill, athreaded bone drill, a conical threaded bone drill, a double bone drill,a stepped bone drill, a bone drill with a triangle cross section, a bonedrill with an asymmetrical cross section, and a Kirschner wire.

The system according to the first embodiment may further comprise ajoining element to join the implant with the corticalis, wherein thejoining element may comprise a material which is fluidizable by means ofthe sonotrode. Further, the joining element may be selected from thegroup consisting of a pin, a conical pin, a dowel, a snap-fit dowel, amulti tooth dowel, a screw, a conical screw, a double pin, a steppedpin, a triangular pin, an asymmetrical pin and a pin having a thickenedhead. Further, the material of the joining element may be selected fromPLLA material or PLDLA material.

A first method of using the system according to the first embodiment,for angularly stable fixation of an implant plate to a bone, comprisesthe steps of preparing at least one hole in the bone; using a jig toprepare the at least one hole in the bone; positioning the implant plateat a desired position at the bone; and joining the implant plateangularly stable with the bone.

The first method may further comprise the step of using the jig to leadmeans for joining the implant plate angularly stable with the bone,wherein the means for joining the implant plate angularly stable withthe bone may be a sonotrode.

The first method may further comprise the step of setting a mark todefine the desired position of the implant plate at the bone.

The first method may further comprising the step of fluidizing theimplant plate material so that the implant plate material flows into theat least one hole in the bone, to join the implant plate with the bone,wherein the implant plate material may be fluidized by means of asonotrode.

The first method may further comprise the step of inserting a joiningelement through the implant plate and into the at least one hole in thebone, to join the implant plate with the bone, wherein the implant plateand the joining element may be melted together, wherein the implantplate and the joining element may be melted together by means of asonotrode.

The first method may further comprise the step of preparing at least onethrough hole in the implant plate simultaneously with the at least onehole in the bone.

A second method of using the system according to the first embodiment ofthe invention, of fracture fixation comprises the steps of placing animplant on the bone, the implant having a first vertical axis normal toa top surface of the implant; drilling a first hole and a second hole inthe bone, the first hole and the second hole forming a first angle and asecond angle respectively with the vertical axis; melting at least aportion of the implant; pushing the melted implant material in the firsthole and the second hole; and allowing the melted implant material tosolidify in the first hole and the second hole to obtain an angularlystable attachment of the implant to the bone, wherein the melting may bedone by applying energy selected from a group consisting of ultrasonicenergy and heat energy, wherein the pushing may be accomplished by aforce exerted by an implement applying the energy.

A third method of using a system according to a first embodiment of theinvention, of fracture fixation comprises the steps of placing a plateon a bone; forming a threaded opening in the bone; melting the plate byapplication of energy and flowing the melted material of the plate inthe first opening and the second opening to form a angularly stableconnection between the plate and the bone upon solidification, whereinthe openings may be formed using a drill selected from a groupconsisting of a threaded bone drill, a conical threaded bone drill and astepped bone drill, wherein the melting may be done by applying energyselected from a group consisting of ultrasonic energy and heat energy,and wherein the flowing may be accomplished by a force exerted by animplement applying the energy.

A system in accordance with a second embodiment of the invention, forfracture fixation comprises a plate, the plate having an opening, theopening being adapted to align with a hole in a bone, and the openingbeing rotationally non-symmetric;

a drill, the drill being adopted to form the opening and the hole in thebone adjacent the plate; a jig, the jig being adapted to guide thedrill, a pin insertable in the opening and the hole; and a sonotrode,the sonotrode being adapted to apply energy to the pin so as to melt atleast a portion of the pin thereby attaching the pin in the bone and tothe plate such that rotational movement of the plate is prevented.

The pin of the system according to the second embodiment may have a borealong its longitudinal axis, wherein the bore may be threaded andadapted to receive a threaded tip of the sonotrode. The pin may have ahead and a body, wherein at least a portion of the body is conical andat least a second portion of the body is cylindrical. The pin may have ahead and a body, wherein at least a portion of the body has projections.In the body of the pin, a slot may be formed.

A method of using the system according to the second embodiment of theinvention, of fracture fixation comprises the steps of placing a plateon a bone; placing a jig on the plate to guide a drill to form theopening; marking the bone to locate the jig on the plate; forming atleast one opening in the plate and the bone, the opening beingrotationally non-symmetric; inserting a pin in the opening; and applyingenergy to the pin to melt at least a portion of the pin therebyattaching the pin in the bone and to the plate such that rotationalmovement of the plate is prevented.

The opening may be formed using a drill selected from a group consistingof a bone drill, a conical bone drill, a threaded bone drill, a conicalthreaded bone drill, a double bone drill, a stepped bone drill, a bonedrill with a triangle cross section, a bone drill with an asymmetricalcross section, and a Kirschner wire.

The energy may be applied in the form of ultrasonic energy or heatenergy.

The pin may be selected from a group consisting of a conical pin, adowel, a snap-fit dowel, a toothed dowel, a screw, a conical screw, adouble pin, a stepped pin, a triangular pin, an asymmetrical pin and apin having a thickened head.

Furthermore, the shape of the pin and the openings may be complimentary,wherein the pin is sized to be a close fit in the openings.

According to a third embodiment of the invention, an angularly stableimplant for fracture fixation, comprises a plate adapted to mount on abone, the plate and the bone having a first opening and a second openingrespectively, the first opening and the second opening beingsubstantially aligned and having a rotationally non-symmetric shape; anda pin shaped to be inserted in the first opening and second opening andcapable of receiving energy to melt at least a portion of the pin,wherein the melted material of the pin is capable of solidifying in thefirst opening and the second opening to weld the pin to the bone and theplate to form an angularly stable implant that does not rotate withrespect to the bone.

In accordance with the first, second and third embodiment of theinvention, the implant or plate as well as the joining element or pinmay be made from a material selected from PLLA or PLDLA, respectively.

Although the invention herein has been described with reference toparticular embodiments, it is to be understood that these embodimentsare merely illustrative of the principles and applications of thepresent invention. It is therefore to be understood that numerousmodifications may be made to the illustrative embodiments and that otherarrangements may be devised without departing from the spirit and scopeof the present invention as defined by the appended claims.

1-66. (canceled)
 67. A system for angularly stable fixation of animplant to a bone, wherein the system comprises a tool for preparing atleast one hole in the bone, a sonotrode, a jig for the tool to preparethe at least one hole in a desired position and/or for the sonotrode,and an implant having a material which is fluidizable by means of thesonotrode, to angularly stable fixing the implant at the bone.
 68. Thesystem of claim 67, wherein the system further comprises a joiningelement to join the implant with the corticalis, wherein the joiningelement comprises a material which is fluidizable by means of thesonotrode.
 69. A system for fracture fixation comprising: a plate, theplate having an opening, the opening being adapted to align with a holein a bone, and the opening being rotationally non-symmetric; a drill,the drill being adopted to form the opening and the hole in the boneadjacent the plate; a jig, the jig being adapted to guide the drill; anattachment element insertable in the opening and the hole; and asonotrode, the sonotrode being adapted to apply energy to the attachmentelement so as to melt at least a portion of the pin thereby attachingthe attachment element in the bone and to the plate such that rotationalmovement of the plate is prevented.
 70. The system of claim 69, whereinthe attachment element is selected from a group consisting of a conicalpin, a dowel, a snap-fit dowel, a toothed dowel, a screw, a conicalscrew, a double pin, a stepped pin, a triangular pin, an asymmetricalpin and a pin having a thickened head.
 71. The system of claim 69,wherein the shape of the attachment element and the hole iscomplimentary and the attachment element is sized to be a close fit inthe hole.
 72. The system of claim 69, wherein the drill and thesonotrode are combined in a single hand held instrument.
 73. The systemof claim 69, wherein the drill is selected from a group consisting of abone drill, a conical bone drill, a threaded bone drill, a conicalthreaded bone drill, a double bone drill, a stepped bone drill, a bonedrill with a triangle cross section, a bone drill with an asymmetricalcross section, and a Kirschner wire.
 74. An angularly stable implant forfracture fixation, the implant comprising: a plate adapted to mount on abone, the plate and the bone having a first opening and a second openingrespectively, the first opening and the second opening beingsubstantially aligned and having a rotationally non-symmetric shape; anda pin shaped to be inserted in the first opening and second opening andcapable of receiving energy to melt at least a portion of the pin,wherein the melted material of the pin is capable of solidifying in thefirst opening and the second opening to weld the pin to the bone and theplate to form an angularly stable implant that does not rotate withrespect to the bone.
 75. The implant of claim 74, wherein the pin isselected from a group consisting of a conical pin, a dowel, a snap-fitdowel, a toothed dowel, a screw, a conical screw, a double pin, astepped pin, a triangular pin, an asymmetrical pin and a pin having athickened head.
 76. The implant of claim 74, wherein the pin has a borealong its longitudinal axis.
 77. The implant of claim 76, wherein thebore is threaded and adapted to receive a threaded tip of a sonotrode.78. The implant of claim 74, wherein the pin has a head and a body, andat least a portion of the body is conical and at least a second portionof the body is cylindrical.
 79. The implant of claim 74, wherein the pinhas a head and a body, and at least a portion of the body hasprojections.
 80. The implant of claim 78, wherein a slot is formed inthe body of the pin.
 81. The implant of claim 79, wherein a slot isformed in the body of the pin.
 82. The implant of claim 79, wherein theshape of the pin and the openings is complimentary and the pin is sizedto be a close fit in the openings.
 83. A method of using the systemaccording to claim 67, for angularly stable fixation of an implant plateto a bone, the method comprising the steps of: preparing at least onehole in the bone; using a jig to prepare the at least one hole in thebone; positioning the implant plate at a desired position at the bone;joining the implant plate angularly stable with the bone.
 84. A methodof using the system according to claim 67, of fracture fixationcomprising the steps of: placing an implant on the bone, the implanthaving a first vertical axis normal to a top surface of the implant;drilling a first hole and a second hole in the bone, the first hole andthe second hole forming a first angle and a second angle respectivelywith the vertical axis; melting at least a portion of the implant;pushing the melted implant material in the first hole and the secondhole; and allowing the melted implant material to solidify in the firsthole and the second hole to obtain an angularly stable attachment of theimplant to the bone.
 85. A method of using the system according to claim69, of fracture fixation comprising the steps of: placing a plate on abone; placing a jig on the plate to guide a drill to form the opening;marking the bone to locate the jig on the plate; forming at least oneopening in the plate and the bone, the opening being rotationallynon-symmetric; inserting a pin in the opening; and applying energy tothe pin to melt at least a portion of the pin thereby attaching the pinin the bone and to the plate such that rotational movement of the plateis prevented.
 86. A method of using a system according to claim 67, offracture fixation comprising the steps of: placing a plate on a bone;forming a threaded opening in the bone; melting the plate by applicationof energy and flowing the melted material of the plate in the firstopening and the second opening to form an angularly stable connectionbetween the plate and the bone upon solidification.
 87. A method forfixing a bone plate to bone comprising: drilling and tapping a pluralityof holes in a bone using a template for locating the holes thereafterplacing a polymeric bone plate having a bone contacting surfaceincluding integral polymeric protrusions onto the bone, the polymericprotrusions aligned with and extending into the drilled and tapped holesin the bone; melting the polymeric protrusions in the dulled and